First comic appearance: Transformers The Official Movie Adaptation (in new Camaro form)

Character description from package back:
Bumblebee and Sam were best friends almost from the moment they first met face to face. as they learned more
about one another, that connection grew deeper and deeper. Now, whether Sam is behind the wheel or standing side
by side with his friend, they work together as a team. Against Bumblebee and his human friend, no Decepticon
stands a chance.

Bibliography of significant appearances: Revenge of the Fallen, movie, comics and novels.